Bisphenol fluorene products, and in particular 9,9-bis-(4-hydroxyphenyl)-fluorene (hereinafter, for brevity referred to as BPF) having the formula ##STR1## are extensively used as monomers in the manufacture of polycondensation products. For example, BPF can be reacted with phosgene to make polycarbonate resins, or else it can be reacted with organic acid dihalides such as terephthaloyl chloride, isophthaloyl chloride, etc., to make polyester resins. Polycondensation products and processes are described, for example, by P. W. Morgan in Macromolecules. Vol. 3, page 536 (1970), and in U.S. Pat. Nos. 3,944,583, 3,968,083, 3,546,165, in GB Pat. No. 1,122,201, in JP Pat. Publ. Nos. 192432/82 and 152622/88 Polycondensation products obtained from bisphenol fluorene products, in particular from BPF, have been found to have good flammability resistance and oxygen indices making them useful, for example, as insulation for electrical conductors, motor slot liners, films and high temperature coatings.
A number of processes have been described in the art for the preparation of bisphenol fluorene products. Generally, such process comprise the condensation of fluorenone with a phenol compound in the presence of acidic condensing agents. BPF can be prepared, as disclosed by P. W. Morgan in Macromolecules, Vol. 3, page 536 (1970), by reacting fluorenone with phenol in the presence of betamercapto propionic acid and anhydrous hydrogen chloride. U.S. Pat. No. 4,467,122 describes a process for the preparation of BPF by reacting fluorenone and phenol in the presence of anhydrous hydrogen chloride, and, as an additional condensation agent, at least one soluble bivalent, trivalent or tetravalent metal halide of a metal selected from the group consisting of Ca, Fe, Ti, Zn, Sn and Al. U.S. Pat No. 4,675,458 describes a process for preparing BPF wherein fluorenone and phenol are reacted in the presence of sulfuric acid (having a concentration greater than 70 percent) and beta-mercapto propionic acid.
In the processes described above, the phenol is generally employed in excess of its stoichiometric amount in order to keep the reaction mixture stirrable. For example, the use of as much as six moles of phenol per mole of fluorenone (U.S. Pat. No. 4,675,458) has been reported as useful. If excess phenol is employed in the reaction, it may be present in the BPF product as an impurity and in the waste materials remaining after recover and purification of crude BPF product from the reaction mixture.
Various methods of recovering the crude BPF product from the reaction mixture and purifying it have been described. For example, the reaction mixture may be diluted with water and boiled until a solid material comprising the crude BPF compound forms. This solid material can then be recovered from the reaction mixture and further purified. Alternatively, the reaction mixture may be steam distilled to remove excess phenol and other volatile impurities prior to recovery of the crude BPF product. In either of these methods, the crude BPF product may be washed with water, dissolved in an organic solvent and crystallized from the organic solvent to further reduce impurities such as unreacted phenol. U.S. Pat. No. 4,503,266 describes a process in which the reaction mixture is combined with hot isopropanol and the resulting mixture is then added to a ten-fold volume of water to precipitate the crude BPF. Alternatively, U.S. Pat. No. 4,503,266 describes a process employing molten phenol in which the reaction mixture is in the form of a crude crystalline paste at the end of the reaction. The paste is then diluted with hot water to form additional precipitate, and the diluted mixture is centrifuged and washed with boiling water to remove impurities such as excess phenol. U.S. Pat. No. 4 049 721 describes a process of extracting impurities such as residual phenol from crude BPF product by mixing the crude BPF product with methanol in an amount sufficient to solubilize all of the impurities, filtering the mixture to remove solid material, adding water to the filtrate which contains BPF as a suspension, heating the resulting mixture and then cooling the mixture to crystallize out purified BPF.
The disadvantage of these recovery and purification processes is that they generate large volumes of aqueous waste containing a low concentration of phenol. These aqueous wastes are environmentally hazardous and the phenol either must be recovered from aqueous waste before disposal or the aqueous wastes must be incinerated. Thus, these processes may result in high waste disposal costs so it would be advantageous to make BPF product using a process which does not generate large volumes of aqueous waste contaminated with a low concentration of phenol compounds.